Presently, image output devices, such as printers, multifunction media devices, xerographic machines, ink jet printers, and other devices produce images on media sheets, such as paper, substrates, transparencies, plastic, labels, or other media sheets. To produce an image, marking material, such as toner, ink jet ink, or other marking material, is applied from a developer to a photoreceptor. The marking material is transferred to a media sheet to create an image on the media sheet.
Toner in developer development housings is subjected to forces which eventually age the toner by impacting external additives into the toner surface. The toner additives are much less effective when they have been impacted into the surface. As a result, the behavior of the material can be affected in both development and transfer.
One solution to combat this problem is the implementation of a toner purge cycle that develops out bands of toner in interdocument zones. Purging of the impacted toner results in dispensing of fresh toner into the development housing to maintain the desired toner concentration and percentage of toner with effective external additives. Toner additive impaction is determined by residence time in the development housing. Machine controls approximate toner residence time by estimating toner usage for each color and making assumptions about the developer composition of aged and fresh toner particles. Unfortunately, the purging of toner is wasteful because it is based on general trends and not on the actual toner condition.
Another solution to the toner aging problem is reducing the abuse of the material within the developer housing. This is commonly referred to as a low abuse housing or gentle development. Unfortunately, although these solutions tend to improve the material abuse problem, they do not eliminate it entirely, and purge cycles are still required.
Thus, there is a need for an apparatus and method that determines toner age in a printing apparatus that reduces the required amount of purge toner to the smallest effective amount.